Mapping Storage Slots to a Set of Storage Units

ABSTRACT

A method includes determining an information dispersal algorithm width number and determining a number of primary storage slots from a number of storage slots associated with a set of storage units deployed across multiple sites, where the number of primary storage slots is equal to or greater than the information dispersal algorithm width number. The method further includes determining a mapping of primary storage slots to storage units. The method further includes sending configuration information to the set of storage units that includes the mapping. The method further includes storing a set of encoded data slices in the primary storage slots in accordance with the configuration information, where a data segment is error encoded into the set of encoded data slices in accordance with the information dispersal algorithm width number and a decode threshold number, which is a number of encoded data slices are needed to reconstruct the data segment.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent application claims priority pursuant to35 U.S.C. § 120 as a continuation of U.S. Utility application Ser. No.17/660,890, entitled “BATCH REBUILDING A SET OF ENCODED DATA SLICES”,filed Apr. 27, 2022, which is a continuation of U.S. Utility applicationSer. No. 16/427,420, entitled “DEFERRED REBUILDING WITH ALTERNATESTORAGE LOCATIONS”, filed May 31, 2019, issued as U.S. Pat. No.11,340,993 on May 24, 2022, which is a continuation-in-part of U.S.Utility application Ser. No. 15/350,672, entitled “CONFIGURING STORAGERESOURCES OF A DISPERSED STORAGE NETWORK”, filed Nov. 14, 2016, issuedas U.S. Pat. No. 10,346,250 on Jul. 9, 2019, which is a continuation ofU.S. Utility application Ser. No. 14/527,139, entitled “CONFIGURINGSTORAGE RESOURCES OF A DISPERSED STORAGE NETWORK”, filed Oct. 29, 2014,issued as U.S. Pat. No. 9,594,639 on Mar. 14, 2017, which claimspriority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional ApplicationNo. 61/924,196, entitled “CONFIGURING STORAGE SLOTS IN A DISPERSEDSTORAGE NETWORK”, filed Jan. 6, 2014, expired, all of which are herebyincorporated herein by reference in their entirety and made part of thepresent U.S. Utility Patent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to storage of dispersed storage encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of another embodiment of a dispersedstorage network (DSN) in accordance with the present invention;

FIG. 10 is a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 11 is a flowchart illustrating an example of rebuilding an encodeddata slices in accordance with the present invention;

FIG. 12 is a schematic block diagram of an example of a batch rebuildingprocess in accordance with the present invention;

FIGS. 13A-13D are a schematic block diagrams of another example of abatch rebuilding process in accordance with the present invention; and

FIG. 14 is a flowchart illustrating an example of a method of a batchrebuilding process in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2 , or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 & 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data as subsequently described with reference to oneor more of FIGS. 3-8 . In this example embodiment, computing device 16functions as a dispersed storage processing agent for computing device14. In this role, computing device 16 dispersed storage error encodesand decodes data (e.g., data 40) on behalf of computing device 14. Withthe use of dispersed storage error encoding and decoding, the DSN 10 istolerant of a significant number of storage unit failures (the number offailures is based on parameters of the dispersed storage error encodingfunction) without loss of data and without the need for a redundant orbackup copies of the data. Further, the DSN 10 stores data for anindefinite period of time without data loss and in a secure manner(e.g., the system is very resistant to unauthorized attempts ataccessing the data).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The DSN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSN memory 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DS managing unit 18 tracks the number of times a useraccesses a non-public vault and/or public vaults, which can be used togenerate a per-access billing information. In another instance, the DSmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generate aper-data-amount billing information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an 10 interface module 60, at least one 10 device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1 . Note that the IOdevice interface module 62 and/or the memory interface modules 66-76 maybe collectively or individually referred to as TO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore, it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5 ); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3 , the computing device alsocreates a slice name (SN) for each encoded data slice (EDS) in the setof encoded data slices. A typical format for a slice name 60 is shown inFIG. 6 . As shown, the slice name (SN) 60 includes a pillar number ofthe encoded data slice (e.g., one of 1-T), a data segment number (e.g.,one of 1−Y), a vault identifier (ID), a data object identifier (ID), andmay further include revision level information of the encoded dataslices. The slice name functions as, at least part of, a DSN address forthe encoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4 . In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG. 8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4 . The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

FIGS. 9 and 10 are schematic block diagrams of another embodiment of adispersed storage network (DSN) that includes the distributed ordispersed storage (DS) client module 34 of FIG. 1 , the network 24 ofFIG. 1 , and a set of storage units 36 of FIG. 1 . Each storage unitprovides at least one storage slot of N storage slots. For example, thestorage unit set includes storage units 1-7 when 8 storage slots areprovided with storage unit 5 providing two storage slots and the otherstorage units providing one storage slot each. The DS client module 34includes an outbound dispersed storage (DS) processing module 84 and aninbound DS processing module 82. The DSN functions to store data as aplurality of data segments, where each data segment is encoded toproduce a set of encoded data slices that are sent to the set of storageunits 1-7, to retrieve the data from the set of storage units 1-7, andto rebuild errant encoded data slices of the plurality of sets ofencoded data slices.

As a specific example of the rebuilding of the errant encoded dataslices, the example begins with FIG. 9 where the DS client module 34detects slice errors to identify the errant encoded data slices. Forexample, the DS client module 34 issues list slice requests to eachstorage unit for at least a portion of a source name range assigned tothe storage unit set, receives list slice responses indicating slicenames of stored encoded data slices and/or the errant encoded dataslices, and compares the list slice responses to identify missing and/orcorrupted encoded data slices as the errant encoded data slices. Forexample, the DS client module 34 identifies missing slices associatedwith storage unit 2 (e.g., data object A, pillar 2, segments 1-3) andcorrupted slices associated with storage unit 7 (e.g., data object A,pillar 5, segments 1-3).

Having identified the errant slices, for each data segment, when the DSclient module 34 identifies an error threshold number (e.g., such that anumber of remaining non-errant encoded data slices is substantially thesame or greater than a decode threshold number) of errant encoded dataslices, the inbound DS processing module 82 obtains a decode thresholdnumber of encoded data slices of the data segment. For example, theinbound DS processing module 82 issues read slice requests 94 to storageunits associated with at least a decode threshold number of storageslots (e.g., to storage units 1, 4, and 5 when storage unit 3 isunavailable, storage units 2 and 7 have errant encoded data slices, andstorage units 1, 4-5 are associated with storage slots utilized to storeat least a decode threshold number of encoded data slices), receives theat least a decode threshold number of encoded data slices (e.g., fromreceived read slice responses 96), and decodes the at least a decodethreshold number of received encoded data slices to reproduce the datasegment as part of reproduced data segments 86.

The rebuilding example continues with FIG. 10 where the inbound DSprocessing module 82 sends the reproduced data segments 86 to theoutbound DS processing module 84. For each reproduced data segment, theoutbound DS processing module 84 encodes the reproduced data segment toproduce rebuilt encoded data slices corresponding to the errant encodeddata slices. For example, the outbound DS processing module 84 dispersedstorage error encodes the reproduce data segment to produce a set ofencoded data slices that includes the rebuilt encoded data slices.

Having produced the rebuilt encoded data slices, the outbound DSprocessing module 84 identifies, for each rebuilt encoded data slice, astorage slot for storage of the rebuilt encoded data slice in accordancewith a rebuilding mapping approach. The rebuilding mapping approachincludes one or more of selecting storage slots associated withavailable storage units and selecting storage slots originally utilizedfor storage of the corresponding errant encoded data slices when thestorage slot original utilized for storage is associated with a storageunit that is now available. For example, the outbound DS processingmodule 84 identifies utilization of a second storage slot associatedwith storage unit 5 and a storage slot associated with storage unit 6for storage of rebuilt encoded data slices associated with pillar 2 whenstorage units 5 and 6 are available storage and storage unit 2 is stillunavailable; and identifies utilization of a storage slot associatedwith storage unit 7 for storage of rebuilt encoded data slicesassociated with pillar 5 when storage unit 7 is available.

Having identified storage slots, for each identified storage slot, theoutbound DS processing module issues a write slice request 98 to astorage unit associated with the storage slot, where the write slicerequest 98 includes one or more rebuilt encoded data slices associatedwith the identified storage slot. For example, the outbound DSprocessing module 84 issues a write request 2 to storage unit 5 wherethe write request 2 includes a rebuilt encoded data slice for dataobject A, pillar 2, and segment 1 etc.

Alternatively, or in addition to, the outbound DS processing module 84updates an association of slice names and identified storage slots. Forexample, the outbound DS processing module 84 updates a dispersedstorage network directory to associate slice names of the rebuiltencoded data slices, the identified storage slots, and identifiers ofthe associated storage units. Alternatively, or in addition to, the DSclient module 34 facilitates migration of the stored rebuilt encodeddata slices from the identified storage slots to original storage slotsassociated with the errant encoded data slices. For example, the DSclient module 34 issues a migration request to storage unit 6 to writerebuilt encoded data slices A-2-2 and A-2-3 to storage unit 2 whenstorage unit 2 is available.

FIG. 11 is a flowchart illustrating an example of rebuilding an encodeddata slices. The method begins at step 110 where a processing module(e.g., of a distributed storage (DS) client module) identifies sliceerrors associated with one or more sets of stored encoded data slices(e.g., receive an error message, obtain slice lists and compare). Themethod continues at step 112, where the processing module, whendetecting that an error threshold number of errors for a set of encodeddata slices has occurred, obtains a decode threshold number of encodeddata slices of the set of encoded data slices from at least a decodethreshold number of storage slots of one or more storage unitsassociated with storing the set of encoded data slices. For example, theprocessing module detects that to slice errors have occurred for a setof encoded data slices, identifies available storage slots andassociated storage units, issues read slice requests to the identifiedavailable storage units, and receives the at least a decode thresholdnumber of encoded data slices.

The method continues at step 114 where the processing module decodes(e.g., dispersed storage error decodes) the at least the decodethreshold number of encoded data slices to produce a reproduced datasegment. The method continues at step 116 where the processing moduleencodes (e.g., dispersed storage error encodes) the reproduced datasegment to produce a set of rebuilt encoded data slices. At least someof the rebuilt encoded data slices corresponds to errant encoded dataslices associated with the identified slice errors. For example, theprocessing module identifies rebuilt encoded data slices for pillars 2and 5 as required rebuilt encoded data slices when the identifiedrebuilt encoded data slices for pillars 2 and 5 correspond to errantencoded data slices of slice errors detected for pillars 2 and 5 of aset of five encoded data slices.

The method continues at step 118, where for each required rebuiltencoded data slice, the processing module identifies a storage slot inaccordance with a rebuilding mapping scheme. For example, the processingmodule identifies available storage slots associated with availableassociated storage units and assigns each required rebuilt encoded dataslice to the identified available storage slots. For each identifiedstorage slot, the method continues at step 120 where the processingmodule issues one or more write slice requests to a storage unitassociated with the identified storage slot. The write slice requestincludes one or more associated required rebuilt encoded data slices(e.g., required rebuilt encoded data slices associated with a commonstorage unit).

The method continues at step 122 where the processing module associatesthe required rebuilt encoded data slices with corresponding identifiedstorage slots. For example, the processing module updates a dispersedstorage network directory to associate slice names of the requiredrebuilt encoded data slices with the corresponding identified storageslots and associated storage units to enable subsequent retrieval whenretrieving particular stored encoded data slices.

When an unavailable storage slot becomes available, the method continuesat step 124 where the processing module determines whether to migrateone or more encoded data slices from the identified storage slot to theavailable storage slot. For example, the processing module compares anoriginal mapping scheme to identify slices that are now stored atdifferent storage units in accordance with the rebuilding mappingscheme.

When determining to migrate the one or more encoded data slices from theidentified storage slot to the available storage slot, the methodcontinues at step 126 where the processing module facilitates migrationof the one or more encoded data slices from the identified storage slotto the available storage slot in accordance with an original mappingscheme. The facilitating includes one or more of retrieving an encodeddata slices, re-storing encoded data slices, and issuing a migrationrequest to at least one of two storage units associated with themigration.

FIG. 12 is a schematic block diagram of an example of a batch rebuildingprocess of a set of encoded data slices (e.g., EDS 1 through EDS 8) in aset of storage units (e.g., SU #1 through SU #8) of a dispersed storagenetwork (DSN). A storage unit of the set of storage units may beimplemented by a storage unit 36 of FIG. 1 . As illustrated, a pillarwidth number (e.g., 8) of encoded data slices (EDSs) are stored in theset of storage units. Note that a data segment of data is dispersedstorage error encoded in accordance with dispersed data storageparameters into the set of encoded data slices. The dispersed datastorage parameters include a pillar width number, and a decode thresholdnumber (e.g., minimum number of encoded data slices needed toreconstruct the data segment).

After storage of a set of encoded data slices, one or more encoded dataslices may need rebuilding. For example, an encoded data slice of theone or more encoded data slices is stored in a storage unit that isunavailable. As another example, an encoded data slice of the one ormore encoded data slices is determined to be corrupt, missing, and/orflagged for rebuilding. In some cases, it may be preferable to defer(e.g., postpone) the rebuilding of the encoded data slice. For example,when more than a decode threshold number of encoded data slices areavailable, waiting until another encoded data slice of the set ofencoded data slices need rebuilding to rebuild the encoded data slicesaves processing costs. For instance, performing a rebuild processseparately for two individual encoded data slices may cost more thanperforming a rebuild process once for two or more encoded data sliceswhile still maintaining a threshold level of reliability. As anotherexample, waiting until a storage unit that is responsible for storing arebuilt encoded data slice is available saves storage and migrationcosts of storing and migrating the rebuilt encoded data slice.

In an example, when one or more storage units are not available that aremissing encoded data slices at the time when a first batch rebuildthreshold is met, the computing device waits until the one or morestorage units are back online, have sufficient capacity to store arebuilt data, or until a reliability threshold (e.g., a second batchrebuild threshold) is met. For example, the computing device waits toexecute a batch rebuild process until only the decode threshold numberof encoded data slices are available. As another example, the computingdevice waits to execute a batch rebuild process until a number ofencoded data slices that are available are within a threshold difference(e.g., 20%, 3 encoded data slices, etc.) from the decode thresholdnumber.

In an example of operation, a set of encoded data slices (e.g., EDS 1-8)are stored in a set of storage unit #1-#8. The pillar width number is 8,the decode threshold number is 3, a first batch rebuild threshold (BRT)is 6 (e.g., PW−2), and a second RBT is 4 (e.g., PW−4). Encoded dataslices shown in white (EDS 1, 3, 5, 6, and 7) are available and encodeddata slices shown in grey (EDS 2, 4 and 8) need rebuilding. When thefirst batch rebuild threshold is met (e.g., 6 or less available encodeddata slices, a computing device delays the batch rebuild process. Forexample, the computing device determines encoded data slices 2, 4, and 8need rebuilding and delays the batch rebuild process. The delayingincludes determining whether target storage units for storing encodeddata slices that need rebuilding are unavailable or whether a secondbatch rebuild threshold is met. For example, encoded data slices 2, 4and 8 are to be stored in storage units 2, 4, and 8, of which storageunits 2 and 4 are unavailable and the second batch threshold (e.g., 4 orless available encoded data slices) is not met. Thus, the computingdevice determines to delay the batch rebuild process until a secondbatch rebuild threshold is met or until one or both of the storage units2 and 4 come back online.

When a threshold number of the target storage units are available, thecomputing device executes the batch rebuild process to produce rebuiltencoded data slices. The computing device then stores the rebuiltencoded data slices in the target storage units. If the second batchrebuild threshold is met (e.g., encoded data slices 2, 4, 6, and 8 needrebuilding) before the threshold number of the target storage units areavailable, the computing device executes the batch rebuild process toproduce rebuilt encoded data slices. The computing device then storesthe rebuilt encoded data slices in the available storage units and oneor more foster storage units.

For example, the computing device rebuilds encoded data slices 2, 4, 6and 8 and determines to store encoded data slices 6 and 8 in storageunits 6 and 8 and determines one or more foster storage units (e.g., adifferent storage unit than originally mapped to store the respectiveencoded data slice that needs rebuilding) for storing encoded dataslices 2 and 4. The computing device then sends a batch rebuild request120 to the respective storage units that are to store the encoded dataslices 2, 4, 6 and 8.

FIGS. 13A-13D are a schematic block diagrams of another example of abatch rebuilding process in a dispersed storage network (DSN) thatincludes a set of storage units 88. The set of storage units 88 includestorage units 36 #1-#7. A storage unit of the storage units 36 may beimplemented by a storage unit 36 of FIG. 1 . The set of storage unitsinclude 8 storage slots (e.g., one in storage units 1, 2, 3, 4, 6 and 7and two in storage unit 5). In this example, the pillar width number is7, the decode threshold number is 3, the first batch rebuild threshold(BRT) number is 5 and the second batch rebuild threshold number is 4.

At time t1 of FIG. 13A, the set of storage units 88 are storing threesets of encoded data slices. The first set of encoded data slicesincludes encoded data slices EDS A_1_1 through EDS A_7_1. The second setof encoded data slices includes encoded data slices EDS A_1_2 throughEDS A_7_2. The third set of encoded data slices includes encoded dataslices EDS A_1_3 through EDS A_7_3.

At time t2, storage unit 7 becomes unavailable (e.g., is offline, isundergoing maintenance, is being replaced, is damaged, etc.). Thus, theavailable number of encoded data slices for each of the three sets ofencoded data slices is 6. Thus, the first batch rebuild threshold (e.g.,5 available encoded data slices) and the second batch rebuild threshold(e.g., 4 available encoded data slices) are both not met for any of thethree sets of encoded data slices stored in the set of storage units 88.

At time t3, encoded data slice A_5_1 is detected to have an error andneeds rebuilding. For example, storage unit 5 responded to a list slicerequest with a list slice response that did not include encoded dataslice A_5_1. As another example, storage unit 5 did not respond withencoded data slice A_5_1 in response to a read request for encoded dataslice A_5_1. As such, the available number of encoded data slices forthe second and third set of encoded data slices is 6 and the availablenumber of encoded data slices for the first set of encoded data slicesis 5. As such, a computing device determines the first batch rebuildthreshold is met for the first set of encoded data slices (e.g., thenumber of available encoded data slices for the first set=the firstbatch rebuild threshold number). The first and second batch rebuildthresholds are not met for the second and third sets of encoded dataslices as they still have 6 encoded data slices available in each set.

Having determined the first batch rebuild threshold has been met for thefirst set of encoded data slices, the computing device determineswhether a target storage unit of target units to store rebuilt encodeddata slices is unavailable. When a target storage unit is unavailable,the computing device determines to delay a batch rebuild process untilstorage unit 7 becomes available or the second batch rebuild thresholdis met. Since the second batch threshold is not met for the first set ofencoded data slices, the computing device waits to execute the batchrebuild process until one or more of a time period as elapsed, thesecond rebuild threshold is met, receiving a command to execute thebatch rebuild process, and the target storage units are available. Notethat if storage unit 7 was online at this point (e.g., the first batchrebuild threshold being met) then the computing device would execute abatch rebuild process to store rebuilt encoded data slices in the targetstorage units.

FIG. 13B continues with the example of FIG. 13A at time t4, where thecomputing device is waiting for the storage unit 7 to become availableor for the second batch threshold to be met (e.g., another encoded dataslice of the first set of encoded data slices becomes unavailable). Thefirst and second batch rebuild thresholds are not met for the second andthird sets of encoded data slices as they still have 6 encoded dataslices available in each set. The first set remains in the delayingphase, as the first batch rebuild threshold is still met, the secondbatch rebuild threshold is not met, and the storage unit 7 is stillunavailable.

Continuing to time t5, storage unit 3 becomes unavailable. As such, theavailable number of encoded data slices for the second and third set ofencoded data slices is now 5 and the available number of encoded dataslices for the first set of encoded data slices is 4. Thus, the firstbatch rebuild threshold is met for the second and third sets of encodeddata slices. The computing device then determines whether a targetstorage unit is unavailable. In this instance, target storage units 3and 7 are unavailable. Thus the computing device determines to delayexecution of the batch rebuild process until one or more of a timeperiod as elapsed, the second rebuild threshold is met, receiving acommand to execute the batch rebuild process, and the target storageunits 3 and 7 are available. In one example, the computing devicedetermines to forego the delaying once a storage unit (e.g., one ofstorage unit 3 or 7) is available.

Also at time t5, the available number of encoded data slices for thefirst set of encoded data slices is 4 which indicates the second batchrebuild threshold is met. Thus, the computing device executes a batchrebuild process for the first set of encoded data slices. The batchrebuild process includes retrieving a decode threshold number of encodeddata slices of the first set of encoded data slices (e.g., any 3 of EDSA_1_1, EDS A_2_1, EDS A_4_1 and EDS A_6_1), reconstructing a datasegment from the decode threshold number of encoded data slices, anddispersed storage error encoding the reconstructed data segment toproduce a new first set of encoded data slices. The computing devicethen sends batch rebuild requests to the set of storage units to storethe new first set of encoded data slices therein.

In this specific example, the computing device generates encoded dataslices EDS A_3_1, EDS A_5_1, and EDS A_7_1 from the reconstructed datasegment. Because storage units 3 and 7 are unavailable, the computingdevice determines foster storage units for encoded data slices EDSA_3_1, and EDS A_7_1. For example, the computing device determines tostore encoded data slice A_3_1 in slot b of storage unit #5 and encodeddata slice A_7_1 in storage unit #6. The computing device the sends EDSA_3_1 and EDS A_5_1 to storage unit 5, and EDS A_7_1 to storage unit 7for storage therein.

FIG. 13C continues with the example of FIGS. 13A-13B at time t6, whereencoded data slices EDS A_3_1, EDS A_5_1, and EDS A_7_1 are stored instorage units 5 and 6. Further, storage unit 7 has been replaced. Thecomputing device then determines to migrate encoded data slices EDSA_7_1 to storage unit 7 in accordance with an updated mapping of EDSA_7_1 to storage unit 7. At this time, the first set of encoded dataslices has 7 available encoded data slices in the set of storage units.The second and third sets of encoded data slices have 5 availableencoded data slices in the set of storage units. Thus, the first, butnot the second batch rebuild threshold is still met for the second andthird sets of encoded data slices. Thus, the computing device waits fora threshold number of the unavailable storage units (e.g., all targetstorage units, # of available target storage units ≥# of unavailablestorage units, a predetermination, etc.) to become available or until asecond batch rebuild threshold is met. In this example, the thresholdnumber of unavailable storage units is all storage units to execute thebatch rebuild process.

Note that when the threshold number of available storage units is met,the computing device will determine to execute the batch rebuildprocess. Note in another the example, the threshold number may bedifferent. As one example, when three encoded data slices needrebuilding in three target storage units of the set of storage units,the threshold number is 2 of the 3 storage units. In another example,when four encoded data slices need rebuilding and three of the fourencoded data slices are for storage in three target storage units of theset of storage units, the threshold number is 1 of the 3 storage units.At time t7, storage unit 3 is replaced and comes back online. Thecomputing device determines to migrate EDS A_3_1 from slot b of storageunit #5 to storage unit #3.

FIG. 13D continues with the example of FIGS. 13A-C at time t8, where thecomputing device determines that the threshold number of target storageunits are available. Alternatively, the computing device determinesthere are no unavailable target storage units. As such, the computingdevice executes the batch rebuild process for the second and third setsof encoded data slices. For example, the computing device retrieves adecode threshold number of encoded data slices for each of the secondand third sets of encoded data slices, reconstructs a second and thirddata segment, dispersed storage error encodes the second and thirdreconstructed data segments into new second rebuilt encoded data slices(e.g., EDS A_3_2, EDS A_7_2) and new third rebuilt encoded data slices(e.g., EDS A_3_3, EDS A_7_3). The computing device then sends the newsecond and third rebuilt encoded data slices to storage units 3 and 7for storage therein.

At time t9, the rebuilt encoded data slices EDS A_3_2 and EDS A_3_3 arestored in storage unit 3 and the rebuilt encoded data slices EDS A_7_2and EDS A_7_3 are stored in storage unit 7. Thus the first, second andthird sets of encoded data slices have the pillar width number ofencoded data slices available in the set of storage units.

FIG. 14 is a flowchart illustrating an example of a method of a batchrebuilding process that begins or continues with step 140, where acomputing device of a dispersed storage network (DSN) identifies one ormore encoded data slices of the set of encoded data slices that needrebuilding. The method continues to step 142, where the computing devicedetermines whether a first batch rebuild threshold is met. For example,the first batch threshold is met when a first rebuild threshold numberof encoded data slices of the set of encoded data slices needrebuilding. For instance, the computing device identifies an encodeddata slice of the set of encoded data slices that need rebuilding. Thecomputing device then determines whether other encoded data slices ofthe set of encoded data slices need rebuilding. When a number of theencoded data slice and the other encoded data slices that needrebuilding is equal to the first rebuild threshold number, the computingdevice determines the first batch rebuild threshold is met.

When the first batch threshold is not met, the method continues to step152, where the computing device queues the batch rebuild process for theencoded data slice. For example, the computing device adds the encodeddata slice to a rebuild list.

When the first batch threshold is met, the method continues to step 144,where the computing device determines whether a target storage unit oftarget storage units of the DSN are available. When a target storageunit of the target storage units is unavailable, the method continues tostep 146, where the computing device delays a batch rebuild processuntil the target storage unit is available or a second batch rebuildthreshold is met.

The method continues to step 148, where the computing device determineswhether the second batch rebuild threshold is met. When the second batchthreshold is not met, the method continues back to step 144. When thesecond batch threshold is met, the method continues to step 150, wherethe computing device executes a batch rebuild process to produce rebuiltencoded data slices. The computing device then sends the rebuilt encodeddata slices to the set of storage units for storage therein. Forexample, when a target storage unit is unavailable, the computing devicedetermines a foster storage unit (e.g., a storage unit that has anavailable storage slot, adding another storage unit to the set ofstorage units, etc.) for storing one or more of the rebuilt encoded dataslices that were mapped to the unavailable target storage unit. For thetarget storage units that are available, the computing device sendscorresponding rebuilt encoded data slices to the available targetstorage units for storage therein.

Note a computing device that includes memory, an interface, and aprocessing module is operable to perform any of the above methods and/orsteps. Further note, a computer readable storage device that include oneor more memory elements that store operational instructions, that whenexecuted by a computing device, causes the computing device to performany of the above methods and/or steps.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method for execution by one or more computingdevices of a storage network, the method comprises: determining aninformation dispersal algorithm width number; determining a number ofprimary storage slots from a number of storage slots associated with aset of storage units deployed across multiple sites, wherein the numberof primary storage slots is equal to or greater than the informationdispersal algorithm width number; determining a mapping of primarystorage slots to storage units of the set of storage units; sendingconfiguration information to the set of storage units, wherein theconfiguration information includes the mapping; and storing a set ofencoded data slices in the primary storage slots of the set of storageunits in accordance with the configuration information, wherein a datasegment of data is dispersed storage error encoded into the set ofencoded data slices in accordance with the information dispersalalgorithm width number and a decode threshold number, and wherein thedecode threshold number of encoded data slices are needed to reconstructthe data segment.
 2. The method of claim 1, wherein the determining theinformation dispersal algorithm width number comprises: obtaining a sitefailure toleration goal number; and determining the informationdispersal algorithm width number based on the site failure tolerationgoal number and the mapping of primary storage slots to the storageunits at each site such that when a number of failed sites of themultiple sites is less than or equal to the site failure toleration goalnumber for a particular time period, the decode threshold number ofencoded data slices are available at non-failed sites of the multiplesites.
 3. The method of claim 1, wherein the determining the number ofthe primary storage slots comprises utilizing a predetermination.
 4. Themethod of claim 1, wherein the determining the mapping of the primarystorage slots to storage units comprises: determining a number ofstorage units at each site of the multiple sites; determining a systemprimary slot distribution scheme; and determining the mapping based onthe number of storage units for each site and the system primary slotdistribution scheme.
 5. The method of claim 1, wherein the determiningthe mapping of the primary storage slots to storage units comprises:assigning, as the primary storage slots, available storage slots fromeach storage unit of the set of storage units at each site of themultiple sites in a substantially even distribution such that each siteof the multiple sites has approximately a same number of primary storageslots.
 6. The method of claim 1, wherein the configuration informationcomprises: storage network addressing information for storing encodeddata slices in the set of storage units.
 7. The method of claim 1,wherein the storing the set of encoded data slices comprises: issuingwrite slice requests to the storage units in accordance with themapping, wherein the write slice requests includes the set of encodeddata slices.
 8. The method of claim 7 further comprises: receiving writeresponses from the set of storage units; determining a failure when lessthan the information dispersal algorithm width number of favorable writeresponses are received within a response timeframe; and in response tothe determining the failure, issuing an additional write slice requestto another storage slot of the number of storage slots, wherein theadditional write slice request includes an encoded data slice of the setof encoded data slices associated with the failure.
 9. The method ofclaim 8, wherein determining the other storage slot comprises:determining a storage unit of the set of storage units that isassociated with a favorable write response of the write responses;determining an available storage slot of the number of storage slotsassociated with the storage unit; and assigning the available storageslot as the other storage slot.
 10. The method of claim 8, whereindetermining the other storage slot comprises accessing a list ofavailable storage slots.
 11. A computing device comprises: memory; aninterface; and a processing module operably coupled to the memory andthe interface, wherein the processing module is operable to: determinean information dispersal algorithm width number; determine a number ofprimary storage slots from a number of storage slots associated with aset of storage units deployed across multiple sites, wherein the numberof primary storage slots is equal to or greater than the informationdispersal algorithm width number; determine a mapping of primary storageslots to storage units of the set of storage units; send, via theinterface, configuration information to the set of storage units,wherein the configuration information includes the mapping; andfacilitate storage of a set of encoded data slices in the primarystorage slots of the set of storage units in accordance with theconfiguration information, wherein a data segment of data is dispersedstorage error encoded into the set of encoded data slices in accordancewith the information dispersal algorithm width number and a decodethreshold number, and wherein the decode threshold number of encodeddata slices are needed to reconstruct the data segment.
 12. Thecomputing device of claim 11, wherein the determining the informationdispersal algorithm width number comprises: obtaining a site failuretoleration goal number; and determining the information dispersalalgorithm width number based on the site failure toleration goal numberand the mapping of primary storage slots to the storage units at eachsite such that when a number of failed sites of the multiple sites isless than or equal to the site failure toleration goal number for aparticular time period, the decode threshold number of encoded dataslices are available at non-failed sites of the multiple sites.
 13. Thecomputing device of claim 11, wherein the determining the number of theprimary storage slots comprises utilizing a predetermination.
 14. Thecomputing device of claim 11, wherein the determining the mapping of theprimary storage slots to storage units comprises: determining a numberof storage units at each site of the multiple sites; determining asystem primary slot distribution scheme; and determining the mappingbased on the number of storage units for each site and the systemprimary slot distribution scheme.
 15. The computing device of claim 11,wherein the determining the mapping of the primary storage slots tostorage units comprises: assigning, as the primary storage slots,available storage slots from each storage unit of the set of storageunits at each site of the multiple sites in a substantially evendistribution such that each site of the multiple sites has approximatelya same number of primary storage slots.
 16. The computing device ofclaim 11, wherein the configuration information comprises: storagenetwork addressing information for storing encoded data slices in theset of storage units.
 17. The computing device of claim 11, wherein thestoring the set of encoded data slices comprises: issuing write slicerequests to the storage units in accordance with the mapping, whereinthe write slice requests includes the set of encoded data slices. 18.The computing device of claim 17 further comprises: receiving writeresponses from the set of storage units; determining a failure when lessthan the information dispersal algorithm width number of favorable writeresponses are received within a response timeframe; and in response tothe determining the failure, issuing an additional write slice requestto another storage slot of the number of storage slots, wherein theadditional write slice request includes an encoded data slice of the setof encoded data slices associated with the failure.
 19. The computingdevice of claim 18, wherein determining the other storage slotcomprises: determining a storage unit of the set of storage units thatis associated with a favorable write response of the write responses;determining an available storage slot of the number of storage slotsassociated with the storage unit; and assigning the available storageslot as the other storage slot.
 20. The computing device of claim 18,wherein determining the other storage slot comprises accessing a list ofavailable storage slots.